My invention relates to a manual transmission having gearing adapted to establish multiple torque ratios in a driveline for an automotive vehicle as it distributes torque from an engine-driven shaft to a torque output shaft connected drivably to the vehicle traction wheels.
A preferred embodiment of my invention is adapted for use with a rear-wheel drive vehicle wherein the torque input shaft for the transmission is aligned with respect to the torque output shaft. As in the case of certain prior art manual transmissions, the present invention is adapted to establish five forward-driving ratios and a single reverse ratio.
An example of a transmission presently known in the prior art is illustrated in U.S. Pat. No. 4,222,281. This transmission comprises a mainshaft which is aligned with respect to a torque input shaft in parallel disposition with respect to a cluster gear shaft. The driven shaft is connected directly to the mainshaft.
Torque delivery gears in the transmission of the '281 patent are journalled on the mainshaft. These mesh with gear elements of the cluster gears of a cluster gear assembly supported on the countershaft. The gears on the mainshaft can be connected selectively to the mainshaft by synchronizer clutch mechanisms, each of which has a shiftable synchronizer clutch sleeve under the control of the vehicle operator. A linkage mechanism, which includes a shift cane, is mounted at the torque output side of the transmission at a remote location with respect to the gearing. A shift rail extends in a direction parallel to the axis of the mainshaft to transfer reciprocating and rotary motion of a driver-operated shift lever element to shift forks which, in turn, actuate selectively the synchronizer clutch sleeves.
The remote disposition of the driver-controlled shift lever with respect to the synchronizer clutch elements in the transmission of the '281 patent makes it necessary to provide a complex shift linkage arrangement. This introduces a transmission calibration problem during assembly because of stack-up tolerances that exist. The arrangement is further complicated by the fact that the motion of the shift lever is controlled by a shift gate and detent mechanism that are located on and supported by a stationary transmission housing independently of the mounting structure for the driver-controlled shift lever.
A manual transmission having a pair of countershafts is shown in prior art U.S. Pat. No. 4,033,200. Unlike the teachings of the prior art '281 patent, the transmission disclosed in the '200 patent has a pair of countershafts each of which supports torque transfer gearing under the control of synchronizer clutches. The mainshaft extends between the pair of countershafts, and the output gear is connected drivably through torque output gearing through the driven shaft as the torque input shaft receives torque from the engine.
A shift linkage mechanism for a transmission of the kind shown in the '200 patent is described in prior art U.S. Pat. No. 4,799,399. This includes synchronizer clutch sleeves that are actuated by synchronizer clutch forks carried by a shift rail. The motion of the shift rail is controlled by a driver-actuated shift lever. The pattern of the motion of the shift lever to accomplish the shifting movement of the shift forks is controlled by a gate and detent mechanism that is secured to a stationary transmission housing. A complex shift linkage mechanism is required to transfer the motion of the driver-actuated shift element to the synchronizer clutch sleeves. This includes a special shift linkage reversing mechanism for actuating a reverse-drive synchronizer clutch.
Prior art U.S. Pat. No. 4,338,828 shows a typical arrangement for establishing the shift path as a transmission shift control lever is actuated by the driver driving ratio selection. This includes a guide plate having a predetermined track and detent arrangement for defining axial positions and rotary positions of the shift rail that is controlled by the driver-operated shift lever.
Prior art U.S. Pat. No. 4,889,003 shows typical synchronizer clutch mechanisms including clutch sleeves for accomplishing ratio changes as torque is transferred through selected gearing supported by the mainshaft and by a countershaft in a transmission of the kind disclosed in prior art U.S. Pat. No. 4,799,399 discussed above.